what kind of thermal pad is needed?

[88serafim88]

I want to perform maintenance on the device, what kind of thermal gasket is needed?

[DGroves]

there is no "thermal gasket",

you have thermal paste and thermal pads for cooling a cpu

most computers use thermal paste google " how to apply thermal paste "

there are many brands/types of thermal paste, again google " thermal paste reviews " 

pick one of the middle/high end pastes that appeals to you

last,.. unless the system is overheating i recommend you do not attempt to change the cpu's thermal paste until you read the above two links and also watch a youtube video on how to remove the cpu cooler in your model computer