Help - invalid TAG name?

[FitzeFusselkopf]

Hi,

I am usind exiftool with Linux Terminal, but I am stucked at a certain point and my terminal skills are very limited. 
Sorry for that and thanks in anticipation.

My target is to reset the "File Modification Date/Time" of several movie files to the value of "Create Date" - so that my video-tool is sorting the files in the correct order.

But when I enter in the directory
exiftool "-File Modification Date/Time" Testvideo.mp4
Invalid TAG name: "File Modification Date/Time"
Warning: Truncated '----' data - Testvideo_Problem.mp4

Even when I only try to read out the parameter, I run into problems
exiftool "-File Modification Date/Time" Testvideo_Problem.mp4
Invalid TAG name: "File Modification Date/Time"

But when I open the file with exiftool Testvideo_Problem.mp4
the parameter is shown as
....
File Modification Date/Time     : 2021:09:20 23:01:55+02:00
....
I tried several variations without blanks, quotation marks, etc. Where is my mistake in thinking?
Thanks a lot.

[StarGeek]

See FAQ #2 and FAQ #3.  Run the command in FAQ #3 to get the actual name of the tag, not the description of the tag.

[FitzeFusselkopf]

Thanks for that. This will help!