Hi,
Aapaka question se yah clear nahin ho raha hai ki aap kis  exam ya website ke liye registration number bhul gayi hain. kripya question clear karen taki apko sahi jankari di jaye. Agar aap engineering ke liye JEE mains ke registration number ke bare me jankari chahti hain to yaha diye link par jakar jankari le sakti hai - https://engineering.careers360.com/hi/articles/jee-main-application-form

yadi AAp apana JEE main registration number yaad nahin hai, to apne email aur mobile nambar se ise fir se prapt kar sakte hain. NTA students ke mobile nambar aur email pate par registration Aur aavedan sankhya ka vivaran bhejata hai. yadi koee vikalp kaam nahin kar raha hai, to JEE main registration number praapt karane ke lie NTA helpadesk se sampark kar sakatee hain.