If you want a heading-like chapter like “Chapter 1”, then you can put:
\cl Chapter
before \c 1
in the USFM.
If you want the order different, something more like Hungarian’s
“1. Fejezet”, where the number comes before the chapter, then in `ptxprint-mods.tex" you would also put:
\def\MakeChapterLabel#1#2{#2. #1}
If you want to just have the number, then the \cl
line could be, for instance \ZWNBSP
(zero width non-breaking space).
For completeness, if you want The First Chapter
as a title, or something similar, then you would put:
\cl The first Chapter
AFTER the relevant chapter number.