My mother takes so many meds. I’m concerned they may be interacting in a way that is not good for her. Who can I contact to check them out?

Schedule an appointment with a reputable Geriatrician (if there is one in your area) and go to the appointment with your mother. A good Geriatrician is the very best resource for overviewing whether an elder's current meds need to be fine tuned. There can be so much more to this than checking simply for drug interactions.
Good luck.

Take the list to your pharmacist and ask for a consult.
Good luck.

Pharmacists can check for potential drug interactions, but they won't be able to determine which meds are really necessary. It gets to be a problem when meds are being prescribed by several different doctors. If you can get a referral to a palliative care doctor, they can review everything and see what's needed and what may not be. My husband had such a review and it was very helpful and informative. Over prescribing in older adults is a major issue.