How to buy a condom in 7 11?

To all filipino mylot users, How will you buy a condom in a convenient store? What will you usually buy first and how would you say that you need a 2 piece of condom? or if you will say that you need a condom would they offer one box or would you buy 2 or 5 pieces? will they ever told you what is your size? by the way is condom have sizes? for example trust condoms have different sizes? I ask these questions just for curiosity... because i never used a condom in my entire life :)