Database archiving option

Have a way to archive the data and exported to sql server files which could be stored on cheaper disk and mounted back into the sql server at a later date if necessary instead of purging the data after x amount of days. We only have so much disk space and if we have a cyber security attack being able to go back 6-12 months is ideal to help find the root cause but due to lack of disk space we can only handle 90 days then we have to purge the oldest data to free up the additional disk space.