I'm stuck on the main quest, it has been awhile since my character has done the main quest and it seems like I have missed placed the copy of volume 3 and 4 of Mythic Dawn Commentaries. Where I can find alternative copies apposed to the ones the game wants m to find?

Volume 4 is only found through the quest to meet someone in the sewers with Baurus, but IIRC there'll be a couple more copies of Volume 3 later, after they're no longer needed.

Giving them to Tar-Meena at the Arcane Uni is actually optional -- what's the last quest update in your journal? You may have already given them to her, or might be able to skip them altogether and move on to one of the next steps.

Jearl (Bruma npc) has some of the books in her basemant. Not sure if vol 4 is there.

Mara

According to UESPWiki there is only one copy of volume 4, on Raven Camoran.