Growth Scans?

I am 33+4 and I have a growth scan today due to not gaining weight. Does anyone know what exactly what will go on. I know they measure baby, is there anything else they will be doing?? This is my 4th baby but never had to have a growth scan with any of my other kids. Also will they give me a 3D pic of him?? Ive seen others posting growth scans and have beautiful pics of there little ones. Just curious 😁 Thanks in advance.