Hi there and welcome to the forums!
You have certainly come to the right place as you will find all you need to know on budgie care here.
Since you are new to budgies, the information on the articles and sticky threads located at the top part of each section of the forums will be extremely useful as you become more familiar and acquainted with the species.
The age on a budgie in most cases can be determined by a few factors, by looking at the budgie and seeing if it has gone through the first moult or not (the presence of the barring on the forehead area will tell the budgie is very young, below 4 months old), the colour on the cere will also give a good clue to the budgie's age and so will the development on the iris rings.
If you are looking into breeding your budgies, given the fact you are new to the budgie world and currently lack in knowledge and real life experience with the species, it's not at all advisable to allow your budgies to breed so soon.
If you have any nesting pots or other nest sites, please remove them from the cage/aviary. Budgies who are below 1 year of age and haven't yet reached adulthood should not be allowed to breed.
Please check these links below and follow the recommendations there: