I am in the same boat, also with a lot of BASF LP35 - all with recorded material on them.
In April, I was given a lot of 15. Of which I have listened to 4. For me, it is always interesting to listen to music that other people favour even if the genres are not what I would normally listen to. Despite that, I am not driven to run them through a bulk eraser.
Someone spent an awful lot of time recording them one song at a time and also compiling a hand written track list for every single reel. That lot of 15 tapes were all recorded at 3.75 so about 60 songs per tape. So give or take about 1,000 tracks.
Last month was a repeat, only worse.
Along with an Akai GX-646 and about eight 10” metal reel of classical music, I was given 50 or 60 7” reels of mostly BASF LP35. Those, I was told, all have “popular music” recorded on them. There was a card file included with them but I haven’t yet deciphered the system of what card goes with what reel of tape. There are many more cards than the 50/60 reels of tape so the time needed to accomplish that is going to be considerable.
I am in my 70’s so it could truly be a lifelong project if I wish to pursue it.