Joseph comments on translation process: he used the Urim and Thummim by the power of God.
Joseph Smith, “Latter Day Saints,” in Israel Rupp, He Pasa Ekklesia. An Original History of the Religious Denominations at Present Existing in the United States. Containing Authentic Accounts of Their Rise, Progress, Statistics and Doctrines. Written Expressly for the Work by Eminent Theological Professors, Ministers, and Lay-Members, of the Respective Denominations (Philadelphia: James Y. Humphreys, 1844), 406, The Joseph Smith Papers website, accessed August 11, 2021
With the records was found a curious instrument which the ancients called “Urim and Thummim,” which consisted of two transparent stones set in the rim on a bow fastened to a breastplate. Through the medium of the Urim and Thummim I translated the record, by the gift and power of God.