Welcome to the Bunnings Workshop community @Noniq. It's great to have you join us, and thank you for sharing your question about wanting to build a 3x3 metre pergola.
It's great that you've decided to build a pergola. One of the best ways to organize your materials is to list them down and visit your local store. I suggest speaking to the Trade Specialist or a team member from the trade department. The trade team member will then be able to determine if all the materials are in-store or if any need to be ordered. Cutting single pieces of timber at the store can be done. However, multiple cuts in large quantities with complex measurements can't be processed in the store. I suggest using a circular saw on-site to make sure all your cuts are done to present job conditions.
If the delivery is quite large the store will have to use a crane truck. I suggest making sure that there is room for the truck to drive into and swing your order onto your property. It's advisable to have an extra pair of hands should you need to offload the timber one at a time.