Many professional photographers state that if your photographs are for online only and you don’t intend to print them, don’t worry about the megapixels and a smartphone camera is fine. The reason for this is that where an image is displayed on a smartphone, computer or tablet screen, the device adapts it for the screen it is displayed on, effectively reducing the information that the image contains (and the number of pixels at the same time) and wiping out the difference between a pro camera with 20 odd megapixels and a smartphone with 5 or six. If you intend to print your photos and use them in promotional flyers etc, then you should pay more attention to megapixels.
As an example, my photograph shown above was taken using a web-cam with a pixel count even lower than that of your old camera. Seen at full size on my pc screen, it is very clearly pixelated. But I wonder if anybody else has noticed at the size it appears on this forum. It was my “No make-up Selfie” on a Facebook post a while ago and nobody noticed any pixelation at all. Neither did I and I KNOW that it is pixelated and would not print up very well at all.
The real difference between a smartphone camera and having a decent camera is in the lens quality and the ability of a better quality camera to alter things like aperture, shutter speed and iso, which will create better exposed and sharper images. If you are interested in using aperture to create an artsy blurred background for example, then a smartphone will not do this for you.
Hope this helps,
Love Sam x