The process of moving the FSMO role from a non-operational role holder to a different DC is called Seizing.
This operation, in most cases, should be performed only if the original FSMO role owner will not be brought back into the environment. Only seize an FSMO role if absolutely necessary when the original role holder is not connected to the network.
Open Powershell as administrator and type “netdom query fsmo” command for checking the current DC which handling the FSMO roles.

Enter the following command for moving the roles from the offline server to the new server “Move-ADDirectoryServerOperationMasterRole-Identity (New server name) -OperationMasterRole SchemaMaster, DomainNamingMaster, PDCEmulator,RIDMaster, InfrastructureMaster -Force” and Enter.

Type “A” for Yes to all and Enter.

After few minutes, the command execution will be done successfully.
For verifying this enter “netdom query fsmo” command again and you will find the FSMO roles are shifted from the old server to the new one.

Finish.