We moved and lost the back up disc for MacBook Pro two years ago. Then my husband got sick and passed away so now I need to learn what to buy for a backup because the MacBook says it hasn’t been backed up for 957 days and I don’t know how to do it. I

You need to know how much data you need to backup, but I use an external Samsung SSD (mine is 1TB), which will likely meet my backup needs for some time. Here are affordable options you can get at your closest Best Buy Store --> https://www.bestbuy.com/site/searchpage.jsp?id=pcat17071&qp=category_facet%3DExternal%20SSDs~pcmcat201300050005&st=samsung+ssd

Then here are directions on how to use Time Machine to backup your MacBook Pro -- > Back up your Mac with Time Machine - Apple Support

I am very sorry for your loss.

https://www.amazon.com/Passport-Portable-External-Drive-Black/dp/B07VP5X239/ref=sr_1_4?crid=2SOD3ZOK0IBVU&keywords=wd+external&qid=1651619932&sprefix=wd+external+%2Caps%2C134&sr=8-4

As soon as you connect that 5 TB drive, your Mac will ask you if you want to use it for Time Machine backups, to which you can answer "Yes." The first backup will take about a day. The backups that follow will be hourly if you keep the drive connected.

You are most welcome. Once you have a drive to backup to, if you need any help, feel free to let us know.

Time Machine Backups are actually easy. Plug the drive in, open Time Machine and tap backup. The one thing you need to remember is once the backup completes, which can take a few hours, is to make sure you Eject the Disk Drive, before you unplug it. I actually made that mistake on my first Time Machine Backup and wound up having to do it all over.

The OP may not need a 5TB drive at all. That's why I suggested they need to know first how much data needs to be backed up.