How to get period and start date from string variable ?

Question

I work on csharp i need to get value of period and Start date from variable productData
so how to get data of start date and period from ProductData string variables using csharp
string productData = Serial No :444909812
ItemType :Electricy
User Name :ahmedsat
Start Date :2021/12/18
Period :30
End Date :2022/1/17

so expected result will be
30
2021/12/18