Change time stamp based on data in filename

Hello,

I couldn't immediately find the answer of my specific question on this forum, so here it is.

I have a lot of files with the name IMG_yyyymmdd_hourminutesec.jpg
I want to use the data of the file names to change the time stamp. How can I do this?

I should probably use the file name pattern in the time stamp category, but no matter which pattern I put, it doesn't seem to recognize it.

To be clear: there are no hyphens between the dates. It's really like: IMG_20170101_103812.

Thanks in advance for the help!