Transferring Funds From First Command to Vanguard

I'm currently in the process of transferring my accounts from Vanguard to First Command, and this process is confusing me.

One of my accounts at First Command is an AMS account, and since the funds in this account are not available in Vanguard, does this mean I will need to liquidate the assets in this account during the transfer process? Does this mean I'll need to pay taxes on this event?