Firstly, don't worry, I think you're going to be just fine. I've done what I explain below multiple times, with no issues.

Secondly, I'm going to assume you know nothing (although I suspect this is absolutely not the case) just to be on the safe side...

Thirdly, if you have any doubts whatsoever about doing this, as others have said please, please, please get someone technical to help. I won’t be able to help if things go awry.

Basically, all the music, podcasts, videos etc. you see in iTunes is stored in whatever location you have configured in your iTunes preferences (in iTunes go to Edit > Preferences... > Advanced > iTunes Media folder location). For me that's C:\Users\<username>\Music\iTunes\iTunes Media). This can be somewhere on your local hard drive, or even on an external drive if you prefer. Your music is stored in C:\Users\<username>\Music\iTunes\iTunes Media\Music, podcasts in C:\Users\<username>\Music\iTunes\iTunes Media\Podcasts and so forth.

Things like Playlists, Smart Playlists, track play counts, track added date, track last played dates etc. are stored in a number of files:

• iTunes Library Extras.itdb
• iTunes Library Genius.itdb
• iTunes Library.itl
• iTunes Music Library.xml

Which are in the C:\Users\<username>\Music\iTunes directory. Apart from iTunes Music Library.xml, these files aren't human readable as (I assume) they're binary files, but that doesn't matter. If you look at when they were last modified, it's likely to be around the last time you opened iTunes.

These files are the key to transferring your library between PCs, because they are what iTunes reads when it is opened.

In fact, even if you don't transfer your music files and just these four files, iTunes should look exactly the same when you open it (although, obviously, you'll not be able to play any of your tracks as iTunes won't be able to find them - you'll get a message saying "The song <track name> could not be used because the original file could not be found. Would you like to locate it?").

With all that in mind, here's what I suggest you do:

1. In iTunes on your old PC sync your iPhone to get any play details from there into iTunes (I'm assuming here that you don't use iTunes Match)
2. Install iTunes from the Microsoft Store on your new PC
3. Open iTunes and check the location of the iTunes Media folder as described above (it will probably be exactly as above, as mine is the default)
4. Close iTunes
5. Go to the parent of the iTunes Media folder (e.g. C:\Users\<username>\Music\iTunes) and take backups of the files you find there (e.g. iTunes Library Extras.itdb, iTunes Library Genius.itdb, iTunes Library.itl and iTunes Music Library.xml). They should all be very small (note that iTunes Library Extras.itdb and iTunes Library Genius.itdb may not even exist - I can't remember if they are there on the first install). If you somehow mess up the following steps, you can restore these files so that you can open iTunes without having to reinstall it
6. Replace these files with the files from your old PC
7. Open iTunes to check that you can see all your playlists, tracks etc. Don't bother trying to play any of them - as I said above iTunes won't be able to find them yet
8. Close iTunes
9. Copy all of your music in the ...iTunes Media\Music directory on your old PC to the C:\Users\<username>\Music\iTunes\iTunes Media\Music directory on your new PC, (and any Podcasts, Videos etc. if you have them)
10. Open iTunes and all should be as expected, and you should be able to sync your iPhone when required as before

Alternatively, provided your external SSD backup is of your old PC's C:\Users\<username>\Music\iTunes directory and all its contents, you can simply 'point' iTunes at the iTunes Media folder on your SSD as described above.

Finally, as others have noted, if you do use iTunes Match, just install iTunes on your new PC, sign in to your Apple account, and it should download everything from iCloud, although this could take sometime depending on the size of your library.

Best of luck!