I've been using adapalene on my face for my acne for over a year. I want to get a chemical peel to help with scars.

Ask your dermatologist if you should discontinue your adapalene and if so for how long before and after a scheduled peel.  You may not have to stop before a light glycolic or salicylic acid peel,  but would likely want to stop a few days to a week before a medium TCA or Jessner/TCA.  If you are scheduled at a spa or with an aesthetician, its best to stop retinoids like adapalene a week prior to your appointment and be sure to let her know you've been using it so she can adjust the concentration and/or length of exposure time and/or passes of acid applied.  

This is an interesting question. It is hard to give a very specific answer
without seeing your scars, knowing how long you have had them and what type of
scarring you have (rolling, pitted, ice pick, etc.).

You mention that you are on adapalene. This is actually a medication of active
acne. Certain peels can help with active
acne.

If you actually have scars that have been there for some
time then a filler is one of the most effective way to improve them. The FDA approved filler that works great for
rolling acne scars is Bellafill.
Sometimes a treatment like excision and another treatment called
subcision are necessary as well.

I hope that helps.

Best regards.