First of all, the picture is quite horrible. Secondly, even if it was a good picture, its pretty impossible to say because DMT varies in density by at least 3x depending on crystallization and so on. Also, as you will see, method of smoking will make a huge difference, so we cant really talk about 'hits' because in an innefective method of smoking, 150mg will get you some funny feelings, and with another, 25mg will transport you to another dimension. How are you thinking of smoking/vaporizng it?
In the long run you should definitely get a scale. Its very cheap, to get a milligram or 10mg scale, just look on ebay or similar.
From how much mimosa was that, and how many pulls?