Wordpress website link to Booking.com

Hi

I am hoping to get some advice.

I administer a Wordpress website for a customer who runs a public house with accomodation (4 double rooms). For this I set up a "stand alone" basic booking plugin (https://en-gb.wordpress.org/plugins/advanced-booking-calendar/) for him. Although this currently works successfully he would now like to add his property to Booking.com and be able to keep his bookings in sync. I believe I would need to upgrade the plugin to a pro version, which contains iCal functionality to acheive this or is there a better way of handling this? Also what would be the process steps I'd need to take in order to achieve this?

Many thanks

Jim