Converting t3a medium to t4g medium EC2 Instance

Question

I am trying to convert t3a.medium to t4g.medium instance getting below error.

't4g.medium' is not a valid instance type for instance 'i-xxxxxxxxxxxxxxxx' of architecture 'x86_64'

Is there any way to find the right instance type? I did some research but did not find anything related, no reply from the AWS support form.

I want to convert all my t3a and t3 type instances to the t4g type instance, any clue to fix this problem will be really helpful.