If your primary goal is ROAS, then the most important metric you have in your planning phase is current sales volume.
The reccommended metric to find out would be the current $/store/week. Then, when planning your campaign you can multiply that number by your target sales lift to determine what your ROAS would be.
For example, if you are selling $1,000 per store per week, and you expect a 3% sales lift, then you could spend $30/store/week to achieve a $1.00 ROAS.
If you have a new item or low sales volume, Pathformance recommends focusing on sales lift % as a better indicator of success. Or finding a way to increase the volume of business supported by the campaign.
If ROAS is unlikely, you may want to leave it off the final report in order to focus the attention on the sales lift %.
If you have any further questions, please contact your Pathformance team member for assistance.