First Right click on Tally 9.0 Icon and go to "properties"

Now Click on "find Target"

Now run the application "tally7.2migration"

a window will open, under that select "migrate data"

enter the path where the data of tally 7.2 is saved

and select the company which u want to migrate.

when migration is completed, a window with "migration completed" will open,

now check the statistics.

now cut the data from tally 7.2 folder and paste in tally 9.0 folder.