Is the language $\{a^n b^m \mid 2n + 3m \le 1000 \}$ regular?
The language is finite and, as such, it is regular (all finite languages are regular).
To see that the language is finite, notice that the maximum length of each word in $L$ is upper bounded by $500$.
Indeed, if $w \in L$, and $n$ (resp. $m$) is the number of $a$s (resp. $b$s) in $w$:
$$
2|w| = 2(n + m) \le 2n+ 3m \le 1000.
$$