Latest version to support MySQL 5.1.69 ib* files
You should be able to load it with 5.5. As a general rule, next version up should always work. You should be able to run mysqldump from there, or run mysql_upgrade to keep it as is for 5.5. Then if you want to upgrade from there, you have to go up to 5.6 and run mysql_upgrade again. Repeat for 5.7 and 8.0 depending on how far you need to upgrade.