the simplest way I would do it is to create a new column, lets call it ElevationINT, that is short-integer or long-integer (depending on which values you have in your initial data).
I would then just do a simple Field Calculator on ElevationINT using the values from the Elevation column. All the integer values will be copied as is, however all the floating numbers will be rounded-up/down depending on the decimal values
100m -> 100m | 100.6m -> 101m | 100.4m -> 100m
If you only want to not see the decimal values, you can right-click the column head, go to properties window, then the numeric subwindow, and on the Numeric tab, set the Number of significant digits to 0. It should be like the attached image.
A third option is to strip all the values behind the decimal mark, which will require a bit of Python scripting: 134.9m -> 134m
Do a field calculation on the ElevationINT column and run the FieldCalculator with the folowing pre-logic code in the codeblock and then call the function in the Field Calculator input:
test = str(x)
if test.find('.') != -1:
val = test.split('.')
See the image for an example of this type of field calculation.