GST AUDIT conduct cost Accountant

Yes Cost accountants are eligible to conduct GST audit u/s 35.

Yes, Chartered Accountants and Cost Accountant both are eligible to conduct GST audit.
if Your turnover is more than 5 Cr in F.Y 2018-19 than GST audit is Compulsory for that year...

As per the Provision of Section 35(5) of the CGST Act 2017 read with Rule 80(3) of the CGST Rules 2017, GST Audit can be conducted either by a practicing CHARTERED ACCOUNTANT ( CA ) or COST and MANAGEMENT ACCOUNTANT ( CMA ).

And for FY 2018-19, GST Audit was made Mandatory only for those taxpayers whose Aggregate Turnover "Exceeds Rs. 5 crores" vide Notification No. 16/2020 - Central Tax, dated 23rd March 2020. [ A new Proviso was inserted to Rule 80(3) of the CGST Rules 2017 ].