Figure 6-14 on page 6-19 of the Claris Resolve User's Guide shows a database that will find on numeric entries. The example shows entries of 18 mm, 30 mm, etc.
The database find command will not find the examples as shown in the book unless you delete "mm" from the entries.
However, for other files this might not always be the case. The numbers in column "C" could have a Custom Format.
To illustrate, select a small range of cells and fill with numbers (Cmd-L). Choose Format > Numeric > Custom Format, type #" mm" into the dialog box and click OK. The numbers will be formatted like you see on page 6-19, and you will be able to find them as shown in the example.