help with newbie game pass vs gold etc - my 3 month code convert to 1 month game pass?

Game Pass isn't just trials. You have access to the full games in the library as long as they are still a part of Game Pass (games get removed from time to time). As long as the membership is active you basically own any game in the Game Pass Library.

Based on the pricing you gave for your Game Pass code it sounds like you actually activated a Game Pass Ultimate code. (US prices are $1 initial price and $15 /month). This membership is actually Game Pass and Xbox Live Gold (online gaming) rolled into one.
If that is the case you should already be able to play online.

The Gold code you're entering is probably just extending your Game Pass Ultimate membership. Go to

https://account.microsoft.com/services/ and you should see the memberships you currently have active.

Did he gift you ultimate game pass or 1 year of gold? Since there is a 1:1 conversion ratio for a normal gold or game pass to Ultimate game pass. For example if you were to redeem a 3 month game pass code while you have ultimate it would convert to a little
over a month in ultimate.

A 3 month game pass code (or gold code] would convert to 2 months of ultimate.

My name is Fernando I'm an independent consultant, I'm happy to help.

I'm going to pass on the information about the new conversion rules:

1-Xbox Live Gold and PC Game Pass Conversion Ratio: Remaining time will be converted to Xbox Game Pass Ultimate time at a 3:2 ratio and rounded up to the next full day. For example, any remaining 90 days of Xbox Live Gold or PC Game Pass will convert to 60 days of Xbox Game Pass Ultimate.
2-Xbox Game Pass Console Conversion Ratio: Remaining time will be converted to Xbox Game Pass final time at a 4:3 ratio and rounded up to the next full day. For example, any remaining 90 days of Xbox Game Pass for Console will convert to 68 days of Xbox Game Pass Ultimate.
3-EA Play Conversion Ratio: Remaining time will be converted to Xbox Game Pass Ultimate time at a 3:1 ratio and rounded up to the next full day. For example, the remaining 90 days of EA Play will convert to 30 days of Xbox Game Pass Ultimate. Gold to Ultimate
1 month of Gold –> 20 days of Ultimate
3 months of Gold –> 50 days of Ultimate
6 months of Gold –> 81 days of Ultimate
12 months of Gold –> 4 months of Ultimate
24 months of Gold –> 6 months of Ultimate

Xbox Game Pass for Ultimate

1 month of Xbox Game Pass for Console –> 22 days of Ultimate
3 months of Xbox Game Pass for Console –> 68 days of Ultimate
6 months of Xbox Game Pass for Console –> 135 days of Ultimate
12 months of Xbox Game Pass for Console –> 9 months of Ultimate
24 months of Xbox Game Pass for Console –> 18 months of Ultimate

PC Game Pass for Ultimate

1 month of PC Game Pass games –> 20 days of Ultimate

EA Play for Ultimate

1 month of EA game –> 10 days of Ultimate
6 months of EA game –> 40 days of Ultimate
12 months EA game –> 2 months Ultimate

Hope I helped and see you soon

It depends on what you did.

If you had regular Gold and/or Game Pass and added Game Pass Ultimate, it converts at a ratio of 1:1. So for example, if you have 8 months of Gold and add 1 month of Ultimate, you'll have a total of 9 months of Ultimate.

If you already have Game Pass Ultimate and you add standard Gold/Game Pass, it's converted at a ratio of 3:1. So if you had 6 months of Ultimate and add a 12 month Gold card, the Gold would convert to 4 months of Ultimate and you would have 10 months of Ultimate.