en_tn_condensed/rom/15/19.md

by the power of signs and wonders, and by the power of the Holy Spirit

You can translate this double negative in a positive form. Here "these are things" refers to what Christ has accomplished through Paul. Alternate translation: "For the sake of the obedience of the Gentiles, I will only speak of what Christ has accomplished through me in my words and actions and by the power of signs and wonders through the power of the Holy Spirit" (See: rc://en/ta/man/translate/figs-doublenegatives and rc://en/ta/man/translate/figs-explicit)

signs and wonders

These two words mean basically the same thing and refer to various kinds of miracles. (See: rc://en/ta/man/translate/figs-doublet)

so that from Jerusalem, and round about as far as Illyricum

This is from the city of Jerusalem as far as the province of Illyricum, a region close to Italy.