My mid-2015 MacBookPro will not boot up, can I remove the internal hard drive and back up my data that way?
Yes indeed. Here is a kit that would get you a new drive and a sled to do data recovery on the old drive.
If you just need the sled, that’s cheaper. Or you could pay a recovery service to do all the work.
For DIY recovery, Data Rescue is amazing and great value for what it does.