How To Convert DataTypes In VB

I am working on a produce inventory database in my VB Express program. I have a form on the bottom and a spreadsheet at the top. I want to enter all the data in the form and have that data automatically transferred as a group to the spreadshet in the upper part of the page when I press a button.

I know that there's an insert function. I set it up correctly. The problem is that I have to convert the textbox, which contain string data, to the datatype used in the database spreadsheet. HOw do I use CAST or do this?

Here's the function I am using:

Me.TableAdapterManager.InventoryTableAdapter.Insert(IDTextBox.Text, fruitName, unitprice, unitsize, unitIn, unitTransit, unitOut)

Evernything is a string cause the data is coming from a textbox, I need to convert it to the datatypes used in the database.