Thanks so much! It worked!
After fixing the wp-settings.php file, it gave the same error with a different page. So I did the same. In total, there were 6 files I had to go through, but it let me login after I fixed each of them.
Again, thank you!
nvm, I figured it out. I had to edit the theme-shortcodes.php file that is a part of the theme.
I changed
$args = array(
'post_type' =>'attachment',
'numberposts' => $number,
'post_status' => null,
'post_parent' => get_the_ID(),
'orderby' =>'menu_order',
'order' =>'DESC'
);
to
$args = array(
'post_type' =>'attachment',
'numberposts' => $number,
'post_status' => null,
'post_parent' => get_the_ID(),
'orderby' =>'ID',
'order' =>'ASC'
);
under “// Gallery”
