You can find the Irish Regiment pack in the Regiment Packs section of the Guts & Blackpowder gamepass shop; the official community wiki lists Regiment Packs as the in-game packs available, and pack pages show they are purchased as Roblox gamepasses.

If you mean the specific Irish regiment included in a pack, the exact pack number isn’t confirmed by the results I could verify here. The safest way to check is in the game’s shop or the unofficial wiki’s Regiment Pack pages, which list the regiments contained in each pack.

A quick clue from the available sources: Regiment packs are map-dependent, so even after buying one, you may only see that regiment on certain maps.

Where to look

  • In the Guts & Blackpowder in-game shop under Regiment Packs.
  • On the unofficial wiki’s Regiment Packs category for the full list.
  • On individual pack pages to see which regiments each pack unlocks.

What I could verify

  • Regiment Pack One is a gamepass.
  • It costs 150 Robux and includes three regiments, though none of the retrieved snippets identify an Irish regiment in that specific pack.

TL;DR: check the Regiment Packs section in-game or the wiki’s Regiment Pack pages; that’s where the Irish regiment pack should be listed if it’s currently available.