You do not need to manually combine the files. The extraction process handles this for you. However, if you are using a file splitting tool like HJSplit, you will need to use its "Join" function to reassemble the parts before extraction.
If you are attempting to locate or open a file with this name, exercise extreme caution: pipsizzz028rar 2021
If you're hunting for a file labeled "2021," this is the most important section for you. Here’s why: You do not need to manually combine the files