The key things when you’re purchasing Mānuka honey is to always look at the label. On the label, it will have either a UMF™ number which will be from 5 up to maybe as high as 20 or even 26. When it has UMF™, that is a quality standard that is in place to ensure that the honey meets and has been tested.
The MGO number that is sometimes also seen on a pack of Mānuka Honey is a similar thing, but it isn’t regulated as closely as the UMF™ number. The UMF™ is checked from shelves all around the world to make sure that, that honey in those jars meets that level of antibacterial activity.
Here's some articles to help you educate yourself some more: