Here's what I came up with. If anybody sees something that needs to be tweaked, please let me know ASAP. This is going into a released app so I need to get it shipped as soon as I can.

 func update_Foreign_Key()
    {
        let the_Version = ModelData.get_Current_Version()
        var theArray = [get_Case_XRef]()
        
        if the_Version == 6
        {
            do {
                try Database_GRDB.shared.databaseConnection!.read { db in
                    theArray = try get_Case_XRef.fetchAll(db, sql: "SELECT * FROM Case_Supplies_Media")
                }
            } catch {
                print("Getting the values from table Case_Supplies_Media failed! (AppDelegate) \(error)")
            }
            
            do {
                try Database_GRDB.shared.databaseConnection!.write { db in
                    try db.create(table: "Case_Supplies_Media_x") { t in
                        
                        t.column("SupplyID_XRef", .integer) .primaryKey() .notNull() .references("Supplies_DVD_List")
                        t.column("CaseID_Supply_XRef", .integer) .notNull() .references("My_Cases")
                        t.column("Supply_Count", .integer)
                        t.column("Supply_Type", .text)
                    }
                    
                    // insert into Case_Supplies_Media_x
                    for theKey in theArray
                    {
                        try db.execute(sql: "INSERT INTO Case_Supplies_Media_x (SupplyID_XRef, CaseID_Supply_XRef, Supply_Count, Supply_Type) VALUES (?, ?, ?, ?)",
                                       arguments: [theKey.SupplyID_XRef, theKey.CaseID_Supply_XRef, theKey.Supply_Count, theKey.Supply_Type])
                    }
                    
                    // Drop table Case_Supplies_Media
                    try db.drop(table: "Case_Supplies_Media")
                    
                    // Rename table Case_Supplies_Media_x to Case_Supplies_Media
                    try db.execute(sql: "ALTER TABLE Case_Supplies_Media_x RENAME TO Case_Supplies_Media")
                    
                    // Set the version to 7
                    try db.execute(sql: "UPDATE My_Settings SET Version = :version WHERE SettingsID = :id", arguments: ["version": 7, "id": 1])
                }
            } catch {
                print("Updating the Foreign_Key values failed! (AppDelegate) \(error)")
            }
        }
    }