Find new customers / increase occupancy

Established yoga/wellbeing holiday rereat centre in southern Spain, re-opening after 18 months covid-related closure. Upcoming retreats in October are under-subscribed, so I need to boost occupancy. I've heard that Facebook groups are a cost effective way to engage with an established target audience. Looking for a marketeer with FB skills and love of yoga who understands how to reach my customer demographic and convert likes into sales. I need fast results. The number of extra paying customers I need is relatively small, so for the right person it should be a fairly simple job.