هُم

A word in the Arabic language will either be 1) a verb or 2) a noun or 3) a particle – هُم is a noun

A noun may either be 1) Definite or indefinite 2) Masculine or feminine 3) Singular, dual or plural 4) Nominative, accusative, genitive or fixed

هُم is a suffix (a word added to the back of a word), a possessive pronoun of the third person, masculine, plural

Means ‘them’ when used as an affix after a verb or preposition
Means ‘their’ when used as an affix after a noun

Grammatical analysis of هُم 
ضَمِيْرٌ مُتَّصِلٌ مَبْنِيٌّ عَلَى السُّكُوْنِ 
مَعْرِفَةٌجَمْعٌمُذَكَّرٌمَنْصُوْبٌمَجْرُوْرٌهماَلْغَائِبُضَمِيْرٌمَبْنِيٌّاِسْمٌضَمِيْرٌ مُتَّصِلٌ
DefinitePluralMasculineAccusativeGenitiveRootThemPronounFixedNounAttached pronoun
       Their    
Surah/Below are the 6+ verses in the holy Quran containing the 7+ occurrences of the plural, masculine suffixهُم
Verse
88-6No food will there be for them but from a poisonous thorny plantلَيْسَ لَهُمْ طَعَامٌ إِلَّا مِنْ ضَرِيْعٍ
the messenger of Allah (SWT) Salih (as) said to themفَقَالَ لَهُم رَسُوْلُ اللهِ
91-13“that is the she-camel of Allah (SWT) and her drink”نَاقَةَ اللهِ وَسُقْيَاهَا
however, they denied him and killed itفَكَذَّبُوْهُ فَعَقَرُوْهَا
91-14so, their Lord destroyed them due to their sin and made them equal in destructionفَدَمْدَمَ عَلَيْهِم رَبُّهُمْ بِذَنْبِهِمْ فَسَوَّاهَا
Except those who believe and do righteous deedsإِلَّا الَّذِيْنَ ءَامَنُوْا وَعَمِلُوْا الصَّالِحَاتِ
95-6for them is a reward without endفَلَهُم أَجْرٌ غَيْرُ مَمْنُوْنٍ
their reward is with their Lord, eternal gardens, underneath which rivers flowجَزَآؤُهُم عِنْدَ رَبِّهَمْ جَنَّاتُ عَدْنٍ تَجْرِى مِنْ تَحْتِهَا الأَنْهَارُ
they will abide therein forever, Allah (SWT) pleased with them and they with Himخَالِدِيْنَ فِيْهَآ أَبَدًا رَضِيَ اللهُ عَنْهُم وَرَضُوْا عَنْهُ
98-8that is for who feared his Lordذَلِكَ لِمَنْ خَشِيَ رَبَّهُ
99-6that day mankind will proceed in groups to be shown their deedsيَوْمَئِذٍ يَصْدُرُ النَّاسُ أَشْتَاتًا لِّيُرَوْا أَعْمَالَهُم
100-11truly, that day, their Lord will be well acquainted with themإِنَّ رَبَّهُم بِهِمْ يَوْمَئِذٍ لَّخَبِيْرٌ
105-2did He not make the plan of theirs go astray?أَلَمْ يَجْعَلْ كَيْدَهُم فِي تَضْلِيْلٍ
105-5thus, making them like devoured cropفَجَعَلَهُم كَعَصْفٍ مَّأْكُوْلٍ
106-4who fed them against hunger and secured them against fearالَّذِي أَطْعَمَهُم مِنْ جُوْعٍ وَّآمَنَهُم مِنْ خَوْفٍ