I have a manufacturing unit of Cotton trouser where customer gives me fabric and I have to convert it into trouser. What would be the rate applicable on me 5 % or 18 %?

The services provided by you fall under the category
of job work by virtue of the definition of job work provided
under Section 2 (68) of the CGST Act, 2017. The rate for job
work in relation to trouser, which is a wearing apparel, is 18%.