360 hard drive swap

They are both Xbox 360 console drives.

One is from first gen and the second is from 2nd gen 360s

The X812848-001 are original 20GB drives from the first gen Xbox 360. Not only do they not fit the 360 E, any official 20GB
hard drive from back then would be knocking on 15 years old by now, which in in technical terms is pretty ancient. Hard drives are mechanical, they don't have long lifespans. It's not a question of if they will fail, it's when.

As previously mentioned the official drives for the 360 S and E are 250 GB, 320 GB & 500 GB. Don't buy a second hand one and expect it to last for a long time, it won't.

Note that the 360 also supports external USB drives up to 2TB.

The only hard drive you could install, is the official Xbox 360 hard drive. which comes in sizes of 250gb, 320gb & 500gb.

as long as both are the same style 360 consoles then you just remove the drive from the one and attach/insert it in the other. NOTE: if you have different versions of the 360 console those drives are not interchangeable (fat drive will not work in a slim
model).

There is no legit way to do so. Anything that could be done would violate the terms of service and cannot be discussed here.