so easyy but a bit long:P go to castelia city from the pokecenter go left and enter the 1st street and wait in the line at the shop(theres only one shop in that st so its not that hard to find) and buy as much of the desert that u want and go straight to nimbasa city and pass through the exit to the left and ull find ur self in route 5 there theres a bus go in and sell it to the women and shell give u 2000 for each.

i hope that worked :) its my first time posting a hint so easy one me .

also if u dont want to do this after u have defeated N cheren will be at rout 5 or 10 no sure and then after u battle him he'll go to victory road there u can battle him everyday and he will pay u alot :)