Dear Dilshad Azam,
Greetings! Thank you for posting in Microsoft Community.
Per your description, it seems that you want to export tasks to Excel from Tasks Planner tab in Teams group.
May I know if my understanding of the scenario is right?
If yes, as far as I know, I'm afraid there is no built-in feature within Tasks Planner tab in Teams group which can export tasks. We apologize for the inconvenience caused.
You may try going to Planner home page https://tasks.office.com/, in Hub, find the name of your Tasks Planner, open it, click the 3 dots from ribbon and then click Export plan to Excel. (as shown below)
Meanwhile, I also recommend sharing your valuable feedback to Planner Feedback Community. Our Product Team is in-charge of the site and they are constantly checking the comments and feedback from our customers. Many features have been developed and improved based on users' comment. Thank you for your cooperation and understanding!
If my understanding of the scenario is not consistent with yours, feel free to point it out, I will continue helping you.
Hope you stay safe and healthy always.
Sincerely,
Tina | Microsoft Community Moderator