Convert Date Format %Y%m%d%H%M%S to unix epoch format

I am trying all the methods but I get this error:

I want to convert this format to epoch –> date “+%Y%m%d%H%M%S”

example –> 20240913235959
I also tried other formats such as:
date “+%Y%m%d %H%M%S”
date “+%Y-%m%-d% H:%M:%S”
but every time I pass time to this command it throws an error.
what I want is to convert Date & Time to epoch, the thing is no other format like 2022-11-09T14:41:15.555641007Z can be used?