Use below lines to display the cell value in a text-box and then re-size the text-box as per the length of text

Sub cellvalue_in_textbox()
' display cell value in textbox
Sheets(1).Shapes("TextBox 1").TextFrame.Characters.Text = Range("b3").Value
' autosize the textbox as per the length of text
Sheets(1).Shapes("TextBox 1").TextFrame.AutoSize = msoAutoSizeTextToFitShape
End Sub