In order to download data from 1C 7.7 trade and warehouse to 1C: Accounting 8.2 you need to run
1. Go to your 1C work database: 7.7 Trade and warehouse
2. Select the tab Service->Upload to 1c Accounting->To Accounting (the version you are using)
3. Select the time period you are interested in.
4. Check the boxes you need for what you want to unload from 1C 7: Trade and warehouse
5. Select the path where the uploaded data will be saved.
6. The resulting * .xml file is your data that you can upload to 1C: 8.2 Accounting
Thus, the data is unloaded from 1C 7.7 to 1C 8.2.