Based on what you said you have it sounds like your uncompressed image is around 10mp which is woefully inadequate for that big of a print. Even 21mp would make a poor quality print at that size.
Printing at anything less than 180 dpi will yield a poor quality print and you are well past that. To print 30x40 @ 180 dpi requires about a 39mp uncompressed image, and 180dpi is not even all that good for prints that will be viewed up close.
If you aren't really looking for photo quality and the print will be viewed from several feet away, it might be acceptable, but for a living room print I wouldn't recommend it.
There is a way to create decent quality prints of this size even with a relatively low resolution camera, assuming the subject is stationary like a landscape shot. Put the camera on a tripod and use a lens that gives you a small portion of your overall subject, then pan and tilt your camera taking multiple photos, which you will later stitch together with software. For instance, you start at the lower left portion of your subject panning along the bottom for 3 shots, then you take 3 in the middle and 3 along the top for 9 shots total. You'll want at least a 30% overlap for each shot. For best results, keep the camera in fully manual exposure and focus mode and don't change your camera settings between shots. You'll need some decent photo stitching software like the full version of photoshop, because you don't want the image to be downsampled. This is the poor man's method of getting an ultra high resolution image with a relatively low resolution camera.
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