Yes, you can backup your Chrome Bookmarks. Export them to one HTML file. Copy to a flash drive.
Edit: I don't know what install media you have or how old it is but you can get the latest version of Window 10 using the Media Creation Tool.
Do a clean install per this guide. It's for Windows 8 but the steps are the same for Windows 10. You want to delete every partition currently on the disk before proceeding with the install.
Make absolutely sure you have all your data backed up. The optimal way would be to do a complete disk image of your Windows 8.1 to an external drive using a program like Macrium Refect Free or Aomei Backupper. Both let you create a bootable DVD or USB flash drive to recover the image from the USB external drive to your computer's drive. It would also be a good idea to do an image of your Windows 10 install after installing all your programs and tweaking it.
Edited by JohnC_21, 10 June 2017 - 10:56 AM.