After lots of digging I finally came across this:
https://ww.wp.xz.cn/support/topic/how-to-keep-galleries-work-when-im-importing-content/
I think the issue is that while I have all of the images on the uploads folder in my website directory, they haven’t been imported into WP itself. When I DO import them, they are assigned a different ID number, but the posts still try to find the images in question with their OLD ID numbers.
Unfortunately the solution in the above link won’t work for me as I was previously hosted through wordpress.com and was not able to use plugins, nor am I able to download database files.
Any ideas how to get that database information from wordpress.com? It’s not looking good unfortunately…
Thanks for the suggestion t-p. Looks like the only .htaccess files I could find were:
/public_html/.htaccess
/public_html/wp-content/plugins/akismet/.htaccess
/public_html/wp-content/plugins/under-construction-page/themes/fonts/.htaccess
/public_html_back/.htaccess