The green mesh would have been for the shrimps to stand on. You need to put something in the bag for that. A bit of java moss or any other plant you have, or even a piece of filter wool would do.
Shrimps need something to stand on. I've seen a shop tank full of shrimps with just a half coconut shell for decor. The coconut was covered in shrimps, and the ones that coudn't fit were standing on the shrimps that were on the coconut. There were only a couple of shrimps on the tank bottom, and they were trying to get on the pile.
At the moment, you won't need a heat pad, but if you post any when the weather is cooler, you will need one. When I've had fish by post, the heat pad has been selotaped to the inside of the box with shredded paper or bubble wrap between the pad and bag of fish.