So I am getting a new PC..

I have Morrowind, Oblivion, and Skyrim with mods and save games with thousands of hours of gameplay; id rather not lose this stuff and start over.
How would I go about putting that stuff on my new pc?

Steam stores saves to the "Cloud" so they will be there for Skyrim for sure. The other games you may have to locate the save files and copy them to an external source to be put back on. As for mods, you might have to make a list of all the mods you're using and reinstall them. I haven't done any modding with Skyrim so I'm not entirely sure. I never played Oblivion on PC, but I did play Morrowind with the texture overhauls and transferred them to a new HDD and I was able to keep my saves.

What I usually do for a game that doesn't have "Cloud" saves is reinstall the game exactly how it was and start a new character far enough to create a save point. Then once I've saved for the first time I'll exit the game, locate the new save file and copy all of the files to that folder. It hasn't failed me yet.

Simple. Go to My Documents/My Games/[Insert Bethesda Game Here]/Saves, find the save file, email it to yourself as an attachment.

Even better, get a high-bandwidth ethernet cord and hook up your two computers, load up the machines, and on the machine that has the game installed already transfer the game install folder and the My Games/[Insert gamesas Game Here] folder to the new PC. On the new PC, download the game off of steam and overwrite the install with the transferred install folder. This will basically add all of your mods that you had installed as is. Then drop the My Games folder into the new computer's My Games. You now have the game installed just as it was on your old PC. Run BOSS, Run Wrye Bash, just to be sure, and have fun.

That's what I always do, anyway.

Make a backup with all your saves and mods. Make folders like Morrowind - Oblivion - Skyrim, and put all the related files to each folder separately.

Install all those games exactly as you have done before. Install your mods, install your utilities related to those games, and put your saves on the default save folders, of those games.