各种忍术 (various ninja techniques) can be translated into Engpsh as follows:

忍術 (ninjutsu): ninja techniques
忍法 (ninpō): ninja arts
忍具 (ninjutsu): ninja tools
忍者武器 (ninja buki): ninja weapons
忍者術 (ninja jutsu): ninja techniques
忍者の本領 (ninja no honryō): ninja skills

Keep in mind that "ninja" is a loanword from Japanese and is not typically written in kanji. The term is often written in katakana as ニンジャ.