Looks to me like it would be easier to move the shop…
First make a backup. You can usually use the backup to move the site and some backup plugins even go a step further by offering migration help.
There is a plugin to help create redirects. https://www.ads-software.com/plugins/simple-301-redirects/
There’s also a website to help create redirects https://www.rapidtables.com/web/tools/redirect-generator.html
Back to the method I’d employ?
I would create the second site and migrate everything over then make that work under a subdomain under your present domain… call the sub either Blog or Shop… your choice.
Remove the parts you don’t want from the new site. Now go into the menu(s) on the new site and point the menu items for content back at the old site – back toward the old address using the proper URL. Remember relative URLs on the new site won’t resolve properly or will resolve to content you may have intended to leave on the old site.
From the other (main) site (the one still using the original domain) I would start creating my 301s by just slightly modifying my present domain by adding the sub name. Pretty easy and nothing gets missed because the world doesn’t know about the newer site until they start following the new URLs.
Once you feel you have the content redirects the way you want then double check your menu items on the older site.
Do yourself one more favor here and install the ‘Broken Link Checker’ on both sites. Just in case you missed something.
You can also remove unattached media items but keep your backups handy because the redirected articles may have issues with relative URLs. Leaving the articles for a time might save you those headaches.