Can I delete mysterious Notes files?

I have been cleaning my iMac of thousands of old files in preparation of buying a new Mac or iPad Pro. In Disk Utility I have noticed that the category "Other" is taking up the most space on my HD. I assume that the system software is apart of this category. I have most of my files currently on iCloud. I recently moved them. So for kicks I did a search for .jpg on "This Mac" and low and behold, hundreds of my old jpeg files are still on my computer. The file thread is the following: Username/Library/Group Containers/group.com.apple.notes/Media/(a long string of letters and numbers/file name

I assume that these are files that I at one time had sent to my iPhone using the Notes app(it seems to be the fastest way to send files). I have since deleted the notes that these files were sent via. I assumed that once the notes were deleted that the files were deleted as well, but they are taking up disc space and in a folder that I can't really access. Group Containers is not usually visible in the listing of folders in the hard drive. The files only show up when I do a general search for jpegs. I can see where the files are by the thread listed at the bottom of the finder window. As a test, I dragged one of the files to the trash and it went there. I hit undo to put it right back. I am afraid to empty the trash, however. I don't need these files and would like to get rid of them, but I don't want to do any harm to my system's Library by doing this back door cleaning. My question: are my assumptions about these files correct and do you think I can trash these the way I mentioned?

FYI: My disc space is as following: Apps 11 GB Photos 30 GB Audio 15 GB Movies 45 GB Other 80 GB Available 67 GB

I hope you can understand all of this. Thanks

Dan