Strangely enough the file is saved under the name 'bitcoin.dat' which I think I might have renamed it to label it properly.
The file is from 2012-2013 if that's of any help. And the file size is "80.0 KB (81,920 bytes)". Does anyone know how I can restore it?
Download the blockchain again. That's the only way you'll be sure that you get all the funds within the wallet.
If you're sure your last transaction was made about 2012-2013, you can synchronize till the blocks in that timeframe. It should show you the relevant transactions during that period of time.
I also have a backup for an old Multibit wallet, file extension ".wallet" (Sized 137 bytes (137 bytes)). Which wallet can I use to restore it? I tried Googling a bit and none of the results I found were helpful.
I am like 99% sure I already sweeped these a few years back and just want to make sure I am not leaving anything behind.
Would appreciate any help on this.
Seems like a Multibit Classic wallet file. If you've exported an unencrypted backup, you can restore it by opening it with a text editor/notepad and the private keys should be organized neatly with the corresponding addresses.