RARE TO LEGEND

hi i have any questions:

first: i have weapon d13 rare +3, how can make +5 in this weapon?
what is the elexir for make +, i know if is a legend, i use d13 proof (legend) but if is a rare i don't, i don't have see proof rare d13

second: how transfert my weapon rare to legend?

for information, i have stop silkraod in max lvl 90 and i come back :D

there's a d13 rare proof stone in silk mall.
you can't transfer a rare item into a legend item.