To avoid this normally you would have one domain permanently redirect to the other. By doing this the search engines realise they are really dealing with one site’s worth of content rather the two.
The “easiest and cheapest way to do this” would be to redirect all requests for visionmissions.com to visionbaptistmissions.com - which would save on swapping the Unique IP, buying and attaching a new SSL, and time moving the site files. And it would be functional in 5-10 minutes.
If you prefer “visionmissions.com” to be displayed in the browser you will need to do all the above steps and then set visionbaptistmissions to permanently redirect to visionmissions in order to avoid any duplication penalties.