copying datetime information in jpg-file

[MunichFan]

Hello everybody, first I must say I'm deeply impressed about the functionality of ExifTool with commandlines. As a new user I have a simple problem, but I can't find the appropriate commands.

I have a jpg-file with the following datetime informations:

[File:System]   FileModifyDate                  : 2017:06:01 10:02:00+02:00
[File:System]   FileAccessDate                  : 2017:07:11 15:35:54+02:00
[File:System]   FileCreateDate                  : 2017:06:29 17:16:19+02:00
[EXIF:ExifIFD]  ModifyDate                      : 2017:06:26 16:40:24
[EXIF:ExifIFD]  DateTimeOriginal                : 2017:06:26 14:35:05
[EXIF:ExifIFD]  CreateDate                      : 2017:06:26 14:35:05
[EXIF:ExifIFD]  SubSecTime                      : 869
[EXIF:ExifIFD]  SubSecTimeOriginal              : 756
[EXIF:ExifIFD]  SubSecTimeDigitized             : 756
[XMP:XMP-photoshop] DateCreated                 : 2017:06:26 14:35:05.756Z
[ICC_Profile:ICC-header] ProfileDateTime        : 1998:02:09 06:49:00
[IPTC]          DateCreated                     : 2017:06:26
[IPTC]          TimeCreated                     : 14:35:05
[Composite]     DateTimeCreated                 : 2017:06:26 14:35:05
[Composite]     SubSecCreateDate                : 2017:06:26 14:35:05.756
[Composite]     SubSecDateTimeOriginal          : 2017:06:26 14:35:05.756
[Composite]     SubSecModifyDate                : 2017:06:26 16:40:24.869

All I want to do is to copy the
[File:System]   FileModifyDate 
to the
[EXIF:ExifIFD]  ModifyDate
and
[Composite]     SubSecModifyDate

I tried it by
exiftool -tagsFromFile "ModifyDate<FileModifyDate" test.jpg
but that did not work at all

Next step would be to copy the FileAccessDate and FileCreateDate

Could anyone help me please. Thank you very much in advance.

[StarGeek]

You were close.  You needed the dash before ModifyDate and in this case you don't need -tagsfromfile.  Also, I added the -P to preserve the FileModifyDate, because changing the file will change that timestamp.
exiftool -P "-ModifyDate<FileModifyDate" test.jpg

FileAccessDate can't be directly modified but will be changed automatically when you change FileCreateDate.  It's a useless system tag anyway as it is inactive unless you change some registry entries. 

Composite tags such SubSecModifyDate are tags created and combined from other existing tags.  In this case, there's no need to worry about SubSecModifyDate as it will be changed when you write ModifyDate.

[MunichFan]

truely, it works !!!

I am happy and thank you a lot for the quick and helpful answer