what should i charge? (gbp)

i make adoptables and i want to give an option for people to pay thru roblox now im playing again ..

what should i charge for £5, £10, £15, £20 ⅋ £25 prices in robux? idk the rates and googling just redirects me to dollar conversion which isn’t super accurate > <

help appreciated! thamk u ‹𝟥