Yes, you can. Use a ruler.
You measure them, using a ruler or tape measure or similar.
Dimensions are linear measures whereas the volume is a cubic measure.
There is not an instrument designed to measure the volume of a rectangular box. You would use a ruler or tape measure or similar to measure its linear dimensions and a brain to multiply them together.
You could share what information you did have and then there may be a way to get the missing dimensions. As it is, there is nothing that can be said other than to suggest that you measure them.
The dimensions of the rectangular lot are: 30m by 15m
The word "rectangular" is an adjective, not a noun. So, a "rectangular" cannot exist. The question is like asking for the dimensions of a blue. What you need to do is specify rectangular WHAT! A rectangular pyramid, a rectangular prism, a rectangular dipyramid or some other shape.
A rectangular prism has 3 dimensions. Whereas the rectangle has only 2 dimensions.
It depends on the dimensions of the rectangular prism.
3
length and width
The dimensions of a rectangular plot are its length and width.
When measuring for a rectangular tablecloth, naturally measure the length and width you need. Then, add at least half of the height of the table on both dimensions, in order to allow for overlap.