Before taking up a migration process you need to be prepared with pre-migration, migration, and post-migration planning to avail a hassle-free cloud migration to Microsoft office 365 and the Microsoft 365 migration checklist involves:

Communicate the transition – The internal and external stakeholders need to be prepared in advance before starting out the exchange migration. Communicate the migration plan, time frame, and the day of the cutover migration.
Prepare details of migration – This includes the preparation of on-premises exchange inventory. The number of mailboxes, storage locations, DNS, etc.
Current infrastructure assessment – Read our Office 365 readiness assessment guide.
Ensure the data to be migrated is ready

To know more about Exchange Migration visit, https://www.o365cloudexperts.com/blog/migrate-exchange-to-office-365-using-cutover-migration/