How to create smallest compressed backup of SQL Server databases intended for deletion?

I need to minimize SQL Server storage in preparation to migrate to cloud. There are about 10 databases that are probably 99% junk/ needed for deletion. Maybe 100%. Reporting databases. What's the best way to do some kind of compressed "backup" just for 6 months? ... It's about 500 GBs total ... would the LDF and MDF files be enough? (wouldn't save on storage but can put somewhere cheap). It's something where it's mostly useless but occasionally some fringe case might be needed to bring it online. Not likely but possible. I'm thinking there's probably a sufficient backup option. I don't need point in time or anything fancy. Just "here's the 10 dbs at this date (say today) in case of emergency". These are largely self contained reporting databases - not complicated applications. I understand corruption might be possible somehow, but willing to risk it. This is an embarrassingly old version of SQL Server as well, 2014 if that is relevant.