check the cultures listed. Most plain yogurts use only 1 or 2 bacterial cultures, usually a strain of Streptococcus Thermophilus.
While this is the most important bacteria for early acidification uring the production of cheese, this alone will not produce Emmentaler or any other long aged hard cheese. For this you need something else.
If you use active Greek yogurt (make sure it says live culture, active culture, or something like that) then you get a set of other bacteria in there that will produce your aged flavors. These are lactobacilli. I believe Greek yogurt contains Lactobacillu Delbrueckii which is also the primary bacteria that a lot of Swiss alpine cheeses use to attain their flavor (NOT lactobacillus helveticus, as is commonly reported)
But even this will still not produce Emmentaler. for these, you need p. shermanii, a third cloass of bacteria. This makes the eyes and characteristic bite of an Emmentaler. This will not be had from yogurt, ou will need to buy it or figure out how to grow some from a wild source. (i would recommend buying it)
But for producing an eye-less hard alpine style cheese (such as my Oberlander or its Swiss parent cheese, Berner Alpkäse, or a number of others such as Gruyere, Etivaz, Vacherin Fribourgeois, Appenzeller, etc.) a GREEK style yogurt will work just fine. Though I would recommend re-activating it first, which is to say make a few batches of yogurt until you get suitably strong, consistent results (very often the first batch made from boughten yogurt will be runny, but can be used to make a successful second batch.) This will give you more control over the culture during cheese making.