In case you are going to make a Slack to Teams migration, it might be a good idea to start with a small-scale transfer rather than attempting to migrate all of your workspace data at once.

When you decide to make a migration for a small team, you may want to create all teams’ channels manually, go through all necessary Slack files and upload them to Microsoft Teams, and collect and re-post essential information or messages.

In addition, it might be a good idea to delete irrelevant channels before migration and determine what data you need to transfer.

It may become overwhelming to migrate large amounts of data manually, and vital pieces of information, such as user mapping, attachments, replies, or older messages, might be missed.

A Slack to Teams migration should, therefore, be performed in stages.

It might be a good idea to test the migration on a small scale first, ensure that everything has been transferred correctly, and then migrate the rest of the data in batches.

In order for the original data to remain accessible, it is advisable not to delete any of the slack data before migration is complete.

A free migration tool can greatly reduce the amount of manual work, required for migrating large amounts of data.

The Kernel Slack to Teams Migration tool can help you with migrating channels, direct messages, group chats, files, attachments, and other elements with the possibility of mapping users/channels and choosing what data to migrate.

It can be found here: https://www.nucleustechnologies.com/slack-to-teams-migration/