To create an archive for all mailboxes,
 

Get-Mailbox -Database DB01 -Filter "ArchiveGuid -Eq `$null -AND ArchiveDomain -eq `$null -AND Name -NotLike 'DiscoverySearchMailbox*'" | Enable-Mailbox -Archive


Link to the full article: Exchange 2016/2019 In-Place archiving

 To create an archive for mailboxes, and set the archive to be hosted on a specific database that we could create to dedicate to archive hosting, we can use the “-ArchiveDatabase <Database_Name>” parameter

 

Get-Mailbox -Database DB01 -Filter "ArchiveGuid -Eq `$null -AND ArchiveDomain -eq `$null -AND Name -NotLike 'DiscoverySearchMailbox*'" | Enable-Mailbox -Archive -ArchiveDatabase A-DB01



NOTE: ArchiveDatabases need usually less IOPS than Primary Mailbox databases, because we assume that older e-mails will be less often accessed by users. That’s why if you decide to host Archive Mailboxes long after having sized and deployed your Exchange OnPrem architecture, we recommend hosting Archive Mailboxes on separate, dedicated databases on other idsks.

 NOTE2: However, more databases per server mean more RAM and CPU the server will use to manage, replicate these Archive Databases, even if these are not accessed or used as often as the databases hosting the Primary Mailboxes => I encourage you to plug more databases on your Exchange calculator, just to check the impact of a few more databases on the RAM. Don’t worry about storage or IOPs, just focus on CPU and RAM the calculator is estimating the server will use/need. 

 Here’s the link to the Exchange 2013/2016 Calculator.
For Exchange 2019, the calculator is now included in the Exchange 2019 setup ISO.