Database Transition Filemaker 12 to Cost-Effective System

We have three databases in Filemaker 12 that we have used for many years. They range from very simple to moderately complex. We are getting notifications from Apple that Filemaker 12 will not be supported on their new OS. Given we would have to move to paying a monthly license for Filemaker if we can no longer use 12, we want to migrate these databases to a platform that is will not cost us thousands of dollars a year in licensing fees. We need someone to recommend a new database system for us, tell us what it will cost annually, and then migrate the databases to it please. I have uploaded clones of all three databases. We would like them all migrated to the same system please.