Procedure for Downloading and Installing ASDM for Cisco ASA Firewalls
show version show failover (if applicable) ASDM version must be compatible with the ASA software version. Refer to the Cisco ASA Compatibility Matrix (generally, ASDM 7.x for ASA 9.8+, ASDM 7.20 for ASA 9.20+).
show flash: | include asdm dir disk0:/asdm*