hi Mansawini,

IIEST takes admission based on JEE main, there is no annoucment related to NATA score in their website. 

Apart from jee MAIN, a student must have any one of the criteria fulfilled :

(i) The candidate is within the category-wise top 20 percentile of successful candidates in their respective Class XII (or equivalent) examination of respective stream and Board.

(ii) The candidate has secured minimum 75% (for GEN or OBC-NCL) or a minimum 65 % (for SC, ST or PwD) of aggregate marks in the Class XII (or equivalent) examination of respective stream and Board.  

link: http://www.iiests.ac.in/images/all_pdf2/FINALddBROCHURE2017-18.pdf