Hi @ZainabJ ,
Please try this:
Overview:
test1 folder stores multiple folders named with person name.
test2 folder stores files created by user.
1.get new file properties in test2 folder.
2.list folders in test1.
3.filter folders in test1 which has same name with "Modified By DisplayName" dynamic content about "when a file is created".

The details in Condition:
1.Determine whether the filter result in the above steps is empty, if it is empty, create a new folder.
2.Compose: get the folder path which is used to store the new file with same person name.
Expression in Condition:
empty(body('Filter_array'))
Expression in Compose:
outputs('Filter_array')?['body'][0]['Path']

Thanks for reading!
Rimmon