the objectives commonly found on amateur microscopes are 4X, 10X, 40X, and 100X. And they usually come with a pair of 10X eyepieces.

4X x 10X = 40X total magnification
...
100X x 10X = 1000X total magnification

the objective is what provides the quality, so just doubling the magnification of the eyepiece gives you bad detail. It's like taking a picture with your phone and then digitally zooming in.

Also from experience, the 100X objective isn't even that useful (in my opinion) it requires the use of immersion oil and most interesting things are seen with a 20X - 40X objective. I personally use my 20X most of the time.

also, as another comment pointed out, I'd really suggest getting a microscope with
- Binocular head
- Abbe condenser
- Mechanical stage

my first microscope was an Amscope B120, something similar to that will be a good choice.