Range(Cells(1, 1),Cells(1 + uBound(Array), 1)).Value = Array

This is an edited piece of code from a module I use within Access to
export recordset information to Excel. I haven't tested it directly in
Excel, but it should put you on the right path.

Range(Cells(1, 1), Cells(10000, 1)) =
Application.WorksheetFunction.Transpose(b)

Thanks for your help. I can now copy array  b data in excel sheet
column 1.

How do I copy this excel 10000 cells data back to array c in a
single command.

I'm 95% sure you can't. Use a loop (it'll be a lot faster than writing
to a sheet from an array  with a loop).

You can't copy it into a defined array  item, but if you say:

Dim vData as Variant
vData = ActiveSheet.Range(Cells(1, 1), Cells(10000, 1))

...VBA will create vData as an array like:

vData(1 to 10000, 1 to 1) as Variant

...and if you later say:

vData = ActiveSheet.Range(Cells(1, 1), Cells(10, 1))

...VBA will automatically redimension it as:

vData(1 to 10, 1 to 1) as Variant