Manually inserting image path into postmeta table?

Hello,

Thank you for your time.

I am migrating an e-commerce site over from joomla/virtuemart to wordpress/cart66. I would like to be able to upload all of my product images directly via FTP, then write a php script that would insert all the proper paths into the wp table(s). So far, I have been able to populate (using a php script) the wp_posts table with the products’ titles and descriptions. I have uploaded the images to the same directory where the wp backend puts them. However, I have NOT been able to populate the wp_postmeta table with the right paths to the images (where metakey = ‘thumbs’). There seems to be some code before the image paths, in the postmeta table, that looks like this:

a:1:{i:0;s:63:

I am not sure what this code is for. Do I have to manufacture something like this for each image? If so, how would I do that? Thanks!