Would almost have to be pixels. 1100×350mm can be expressed so many other ways more efficiently. Is it for the web?
Pixlr is good in a pinch.
https://pixlr.com/editor/
1. Open your image
2. select the crop tool (upper left option in the tools panel)
3. Towards the top it will give you options to constrain by aspect ratio. Enter width 11.0, height 3.5 and crop as wide or long as you can.
4. Go to the “File” menu at the top, click “Save” and select your options. Tough to tell without seeing the image what options would be best, but defaults aren’t bad.
Happy to crop it and shoot it over to you if that works better. Send a message here if needed.