Power analysis for time series regression

Hello, I'm trying to determine the sample size I need for a study. In the analysis, I will be including three predictors (score on a questionnaire, time, scorextime interaction) and one outcome variable. I am only using one group of individuals and collecting data at baseline, time 1, time 2, and time 3 (and maybe time 4). This is in a single group of individuals. How can I best determine the sample size needed?

Thanks in advance!