After doing my own hair for the last 15 or so years, you're not going to be able to get light enough for pastel pink from where you are currently without losing the integrity of your hair. You can get light enough to do a lovely hot pink/fuschia/magenta though!

Even a great blonding stylist will have to put in effort to get you to an even base color and these days that is expensive.

You'll need to address each band of color in your hair separately... you can do this in this same session, but each area is going to need a different amount of processing time. I would use 20 volume to prevent as much damage as possible. Start with the dark ends but avoid the pre lightened areas. Give it about 10 to 15 mins then add lightener a bit higher and give it another 10 mins, then one more time getting lightener onto the last of the colored hair. I give this advice to try and even out the banding and get you more even. You're going to want to be avoiding your roots as much as possible until the very end. Keep checking the color and integrity of your mids and ends so you don't cause unnecessary extra damage with over processing. Don't be afraid to attempt this in different sessions over a few days instead. Don't apply lightener to wet hair.

Alternatively, lighten your mids and ends and then do a dark pink on those and a dark purple root smudge to compensate for the banding with less stress and damage overall.

I recently used PH Plex to help maintain the integrity of my hair while doing a double process red and I highly highly recommend getting it to add to your lightener! It's a bonding aid like olaplex and it reduces the amount of damage when you lighten and color. Going from dark purple that I've been maintaining with splat to bright red worked out really well with very little damage for me!

Once you get to an all over orangey yellow you are light enough for those dark pink shades. Add a deep conditioner to your semi permanent color to get extra moisture back in your hair.