Hi Team,
Use below steps to get the SP group users and send an email to each of them :-
1. Initialize 3 variables for GroupMembers , i and userEmail as shown below -

2. Now, send an HTTP request to SharePoint to get users from the respected group, as shown below -

3. Now, set the pre-initialized Array variable with output from the above HTTP request as below.
body('Send_an_HTTP_request_to_SharePoint')['d']['results']

4. Add Apply to each and add 'GroupMembers' in output which we created for array.
5. Set variable userEmail with the email address of user -
variables('GroupMembers')[variables('i')]['Email']

6. Use this userEmail variable in To of Send an Email action and then Increment the variable i with 1 -

You are done !!! An email will send for each of the users of group .
Output -

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Thank You !!!