How to attack long random passwords

[c0nf11s3d]

Good evening within about this post because I too would like to understand on some modern modems the password is 24 alphanumeric characters capital letter lowercase letter and numbers I'm trying with masks and rules in combination with dictionaries but the times are very long an example of my password of my modem:

a5tUWG2F3GjlwNRax0B2AVxH

what method could i use to optimize times?
Or rather which mask and rules do you recommend?
Thank you all.