how to calculate total surface area？🙏🏻?

Frist I let the length be l, height be h, and the width be w. Then there will be a formula to calculate total surface area (SA) of a cuboid:
SA=2lw+2lh+2hw
As a clearer description, total surface area means you just need to add all area of the faces, much easy right? So you can don't use any of formula, just work for a long time to find the area of each faces and add them together. (This is the basic way to calculate) 
For more information, just search in Wikipedia and you will get the answer (also Google XD)
Wiki link: https://en.wikipedia.org/wiki/Surface_area#Common_formulas
Google search link: https://www.google.com/search?sxsrf=ALeKk01QvcY0IatKyz3YbktFQTXalCU5zA%3A1609977873107&ei=EVD2X4KLBpDM-QblpYGIDg&q=total+surface+area&oq=total+s&gs_lcp=CgZwc3ktYWIQAxgAMggIABCxAxCDATICCAAyAggAMgIIADICCAAyAggAMgIIADICCAAyAggAMgIIADoICAAQsAMQiwM6CQgjECcQRhD_AToHCCMQ6gIQJzoFCAAQsQM6BAgAEEM6CggAELEDEIMBEENQgPMFWO_eBmC18wZoA3AAeAKAAYACiAHCDZIBBjQuMTAuMZgBAKABAaoBB2d3cy13aXqwAQHIAQG4AQLAAQE&sclient=psy-ab