If you’re is still looking to copy prefixed tags to metafields it’s something you can do for free with our Ablestar Bulk Product Editor app with just a few clicks.
The app allows you to bulk edit metafields and has ‘placeholders’ which allow you to dynamically insert data from other parts of the product. You can use the ‘SKU Suffix’ placeholder to set a metafield to be the part of a tag after something like “brand=”
Here’s a quick video showing how it works:
The free plan of the app includes 5 free edits every 30 days with no limit on the number of products so that should be suitable for your needs if you just have a couple of tag types you need to move over.
Best,
Daniel