I will mention this even though you said you don't want to involve your old mac: Often, a great way to move an UltraPAK to a new computer, is to simply copy the entire Band-in-a-Box folder to your new computer via an external USB drive. Once you've done that, an important step is to then run the latest full Band-in-a-Box program installer package. Also, install other "non-BiaB" installers (i.e. files that install things to locations other than the Band-in-a-Box folder - HiQ Instruments and Playable RealTracks in particular).

If you don't want to do that, I would use the Install Manager, along with your My Products page:

(1) Run the Install Manager, update to the latest build if necessary.
(2) Find the "Download URL" for the Band-in-a-Box 2023 UltraPAK - click Copy to clipboard. Paste that into the Install Manager. If you have the 2023 Ultra, you do not need to do anything with the 2022 or earlier BiaB packages, just the latest one.
(3) You do however need to install any Xtra styles. For each Xtra styles package listed on your My Products page, Copy the download URL to the Install Manager as above.
(4) From this point it is relatively painless to download and install the items using the Install Manager - however before you 'download and install' the UltraPAK you will want to think of the the best location for your 'download folder', since you need to have a couple hundred GB of free space for the downloaded packages, and then a couple hundred for the install. That's mainly for the benefit of others reading this, as I see your new computer has a large hard drive. But FYI you can download the files to an external drive, delete them when finished downloading, and/or move them later to free space - there are several options.

Andrew
PG Music Inc.