new xbox user , looking to purchase xbox gold /ultimate pass

many thanks for the help..

Yes and no. You can only add up to 36 months at a time, so you would want to add a little bit less than 36 months of gold first. But yes, if you add standard gold first and then purchase Ultimate, the remaining gold will be converted to Ultimate as well.

I agree with Wadski in that if you currently just have a Xbox Gold subscription, you are better off adding additional months to you Gold Subscription or Game Pass first before you convert to Ultimate. If it is your first time converting to Ultimate, the
total months of Xbox Gold plus the total months of Game Pass will be added as your new Ultimate subscription. 12 months of Gold + 3 months of Game Pass will convert to 15 months of Ultimate. If you purchase 3 months of additional Gold membership then you will
get 18 months of Ultimate. Therefore only purchase Ultimate after you convert your subscription.

Purchasing Xbox Game pass Ultimate, cancels your gold membership and game pass membership, and replaces it with ultimate which includes both gold and game pass.

No. If you purchase just Xbox Game Pass, then you would need Xbox Game Pass Core (new name for Xbox Live Gold) to play online multiplayer. If you purchase Xbox Game Pass Ultimate, then it would cancel your Xbox Live and convert it to Game Pass Ultimate and add it on to your Game Pass Ultimate. Any remaining time will convert to Xbox Game Pass Ultimate time at a ratio of 3:2 and be rounded up to the next full day. For example, 90 days remaining of Xbox Game Pass Core or PC Game Pass will convert to 60 days of Xbox Game Pass Ultimate time.