Hi, Elena20. Thanks for contacting us. We'll be happy to help. The data pack is only compatible with the $35 3GB monthly plan. In order to add a pack, you'll need to first add the money to the account. We have two data packs available: $5 Data Pack 1GB, and $10 Data Pack 2GB.
If you need assistance to add a data pack, please send us a private message with your phone number and PIN. To do so, just click on the picture of any Boost Mobile agent and, in the next screen, click "send this user a private message".