How to set actual sales target?

It is a very special question but what i know that the sales target been set odepending on last year sales or according to expectation and market study

the sales process: Leads > Prospects > customers from demand side:1.forecasting the number and specifications of leads in the determined market campaign.2.
how many of these can be converted to prospects and with which marketing methods.3.
forecasting how many of these prospects will become our customers? from supply side: what are minimum, optimum and maximum capacity in our company? by formulating both sides with the available data from the previous periods, setting the actual sales target is possible.

Firstly list your turnover / revenue targets for the next12 months.
You need to know what this figure is, in order to know how many sales you should be making each year.
If you have done a business plan, you can take the figure you used there, or you can work it out by listing all the outgoings of the business including how much you would like to "make" on top of what you need to clear the bills, also note down the pricing of your products or services.
Next you need to work out what your &qaverage" sale value is.
The fastest way to do this is to make a list of the value of your last day’s sales, and then divide that number by the total number of sales.
This is only an approximate figure, but is often fairly accurate.
Then, list how many "average" sales you would need to make over the next12 months, in order to achieve the figures that you got from step one, make a note of this number.
Next, divide the number you wrote down in step3, by12 to get your monthly sales target.
If you want to work to break it down into weekly targets, simply divide the annual number of sales by52, or more realistically48 to allow for bank holidays and other times you may be closed or simply have fewer customers.
If you want to have quarterly sales targets, then you need to divide the number of annual sales by4.