Husqvarna tc85 help (spring strength)

Hi all

I'm new to mx bikes and I recently bought a 2022 Husqvarna tc85. It came with a WP 40-215 G/R rear spring. The problem is that this is far too soft for me. I weight 72kg (160lbs). I am looking at springs but they all have a different Nm rating. Which Nm rating would I require to help stiffen up the rear suspension. Please note that I already adjust the suspension to it's hardest setting. 

Thanks for your help