Upgrading from Craft 3

Sprout Forms is available on Craft 3 and Craft 5 but was never released on Craft 4.

When upgrading other plugins and Craft to their respective Craft 4 releases on the path to Craft 5, leave Sprout Forms in the database and once the codebase is upgraded to Craft 5 the appropriate migrations will be applied. See the upgrade notes in the Sprout 5 docs for more information on upgrading from Craft 3 to Craft 5.