To start with first of all download tally from tally's site.
Run Install.exe in a separate folder tally8.1. Now activate the license of Tally 8.1. To Migrate data from 7.2 to 8.1 it is necessary to have an activated version of 8.1.
Go to Tally 8.1 folder and locate a file migration tool.
Start the tool by specifying the location of Tallt7.2 data which would be in c:tallydata folder where your 7.2 version was installed.
Select a company and migrate. After whole process has ended it would make another fold in same location but with different name.
You can identify the folder easily as it would contain 4 numbers. e.g. Your existing folder would be 001 and new folder would be 0001.
Copy paste this newly created folder in c:tally8.1data and run tally.
You would see the new converted data.

If you face any problem then you can tell me by comment on this article.
plz told me where first i go to migrate my data…..