Your first place to start is use a more uptodate language. What you want to do is possible with the express versions of Visual Studio. Using VB6 is like chaining a steel ball to your ankle before you run a marathon, you've lost before you even start.
Next you should probably learn about database programming and SQL queries.
Barcode scanners are basically serial input devices that can be read the same as a keyboard.
The printer should have it's own drivers, so it'll just be a matter of telling the software to print to it.
Do things in steps and make liberal use of modular programming. Get each part to work as independant sub routines, functions and/or classes before going on to the next part. A flow chart and/or class diagram would be really handy to keep track of what you've done and what needs to be done.
There a great many sites with tutorials and examples. Google will probably be your best friend before you're done. You may even find existing code that does what you want.