When the word “Scripture” is found in the New Testament, it (almost always, see the last paragraph below) refers to the Old Testament.
The New Testament was originally written down in an everyday form of Greek called Koine (pronounced koy-NAY). The Old Testament was written in Hebrew with parts in a related language called Aramaic.
The Hebrew Bible contains all the books found in the christian Old Testament, although the order is different and some books are combined. Also, a few of the books divide the chapters differently than the christian Bible does. Some christian traditions include in the Old Testament additional books called the Apocrypha or additions to some books. In most traditions these books are to be read for life instruction but not for doctrine.
About these 39 Old Testament books, the New Testament says, “All Scripture is inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness;” (II Timothy 3:16)
Probably in the year 68 CE, just before Peter was killed in Rome, he wrote his second and final letter to the christians in some of the same areas where Paul had written letters earlier. Peter does seem to regard Paul’s writings as Scripture: “Therefore, beloved, since you look for these things, be diligent to be found by Him in peace, spotless and blameless, and regard the patience of our Lord as salvation; just as also our beloved brother Paul, according to the wisdom given him, wrote to you, as also in all his letters, speaking in them of these things, in which are some things hard to understand, which the untaught and unstable distort, as they do also the rest of the Scriptures, to their own destruction.” (II Peter 3:14–16)