Many different ways of doing this and which to use depends where you are getting your timestamp, your JMP version and your regional settings.
I'm not sure if JMP will recognize that format so you might have to build it by using different functions. One option is to first build it as something JMP will recognize and then use Substitute (or Regex) to remove unnecessary characters. Format Pattern only works if you have JMP16+
Names Default To Here(1);
date_str = Format(Today(), "Format Pattern","<YYYY><-><MM><-><DD> <hh24><::><mm>");
//using regex
date_cleaned = Regex(date_str, "[^\d]", "", GLOBALREPLACE);
//using subsitute
date_cleaned = Substitute(date_str, ".", "", ":", "", "-", "", " ", "");
Quite often when I'm saving filenames with timestamp from JMP, I will just use Char(Today()) which will then be seconds from 1904-01-01 00:00:00
-Jarmo