Hi @ashishkapur
Please follow the instructions from @OliverRodrigues . In addition, to solve your problem, there are two approaches I would suggest
1. Choose the Power Apps Per plan or Power Pages per pay-as-you-go plan. This will allow you to create one environment. Then you can choose the sandbox environment.
2. This is my favourite
a. Go to https://make.powerapps.com/
b. Choose the right environment
c. Apps > Website > New
d. Type the Name and address and make sure you check the checkbox like below

e. Choose the website record (in your case - your trial power pages site)
This method will bring all your work back to the newly created portal. So you get another 30 days.
It is a laborious process but some joy
Have fun.
Hope it helps.
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