Units are units of measure such as centimetres, grams, litres etc. Place value is so very important and needs to be explored in all its aspects, including positional, additive and multiplicative.
Using base 10 equipment a single cube has a value of one so you would ask questions like how many ones do you have, how many ones make one ten, how many tens make one hundred etc. Use 100s, 10s, 1s as our column headings instead of H T U when moving on to more formal recording.
To be flexible I would refer to the Diennes apparatus single cube as a 'unit' cube. Therefore the unit cube can then adopt whichever value you wish it to be. If the unit cube has a value of one then the stick of ten has a value of 10. If the unit cube has a value of one tenth then the stick of ten has a value of 1. This flexibiity enables pupils to use the multipicative relationship of the different diennes models and provides a tool for working with not just whole numbers but decimal numbers as well. However in terms of place value the positional value of the place to the right of the tens digit, this would be described as 'ones'.