Hello, I'm working with a solid wood countertop for a vanity -it's
1-1/8 x 18" x 28". I've glues up 3 boards to make this, and now want
to plane it flat.

I only have one hand plane, and it's a cheap one from harbor freight.

Seeing as how I spend $45 on this lumber, I'd really like to avoid
mistakes.

Would you kind folks please offer me some suggestions on which type of
plane I need to flatten this?

Lowes is the only box store I've found that offers hand planes, but
'#4' doesn't mean anything to me....

Thanks in advance for your advice!
Fred