1. Check the versions of your source and target MySQL DB and PHP versions
2. Provide your source and target FA versions
3. List any extensions added in FA 2.3.x that may have spawned additional tables / file mods
4. List any custom FA and sql mods done
5. Checkout the FA source dump (backup - list size / open fiscal years) and compare schema with FA 2.4.7+ sql/en_US-new.sql schema.
6. Checkout all the sequential sql/*.sql and sql/*.php file updates after your existing versions
Test it out in a VM / container first. Paid assistance booty can be posted in the Job Offers board.
If all else fails, PM me.