AnyConnect on ASA uses activation keys, not license files. (Except for ASAv which uses Smart licensing.)
If your AnyConnect license is the current 4.x Plus or Apex style license then it is licensed per number of unique users and can be used for multiple ASAs. Each one though needs to have a new activation key (generated from the PAK) to be entered. This can be done from the software.cisco.com portal, traditional licensing page. If the current PAK doesn't appear on your page then you will have to open a case with TAC or email licensing@cisco.com.
If your Anyconnect is the older 3.x (Essentials and Premium) type or 4.x VPN Only 4.x license then it cannot be used on a different ASA except in case of appliance RMA to Cisco.