Both of these Track Packs can be exported to Rock Band 4. Since they’re Xbox 360 links, they would show up as a full track pack on the Xbox 360 purchase history. On your Xbox One, they will show up as DLC for Rock Band 4 instead. To install it, simply go to the Ready to Install section of Rock Band 4 and all of the DLC should be there after a few minutes.
Also, if you see errors like “Ooops, can’t see the page” try again. I had to try it around 5 or 6 times before it worked on my phone. Just did it for a friend on a computer and it worked right away. These packs new go for around $20-$40 on eBay, so can’t go wrong with free exports!
Rock Band Metal Track Pack https://marketplace.xbox.com/en-US/games/offers/0ccf023f-0000-4000-8000-000045410829
Rock Band Country Track Pack https://marketplace.xbox.com/en-US/games/offers/0ccf0240-0000-4000-8000-000045410829
While you’re here, as a friendly reminder. The Rock Band 3 Export will expire on December 1st, 2020. So if you’re looking to bring all of your Rock Band 3 (disc) songs to Rock Band 4, you can purchase the Export Key for $14.99. If you purchase it before December 1st, you’re good to go since you can keep the songs and export them at any time.
Rock Band 3 Export Key