Working out est 1rm

Hi, I just on running the first week of The Bridge 1.0 and I am wondering the equation to get my estimated 1rm. Say for example, my Pause Squat I got 75kg x 4 @9 x 1. Where do I go from here to get 1rm. Also, am I right in thinking that in week 2 even if my weights stay the same, my etimated 1rm will go up due to an increase in volume? Sorry if this is already answered but never used This type of equation to gauge progress coming from SS programming.

thanks.