How do I extend a trial period for Azure AD Premium 2

you can probably get months of AD P 2

https://learn.microsoft.com/en-us/answers/questions/1060643/how-do-i-extend-a-trial-period-for-azure-ad-premiu?source=docs

activate AD P 2 for one month

then after 1 month, activate enterprise mobility for another trial month, which includes P 2