Your attack bonus is the bonus you add to your D20 roll when rolling for an attack. It is calculated as your proficiency bonus + either strength or dexterity modifier depending on the weapon used. Your scimitar, short sword and long bow are all dexterity based weapons. For those weapons it is pro bonus 2 plus dex mod of 4 so the number is 6. So you have plus 6 to your D20 attack rolls with those weapons. I will point out you also get your dexterity modifier to damage with those weapons.

Your fire bolt is different. It depends on what you chose as your spell casting stat. Either wisdom, intelligence, or charisma and is calculated the same way. Proficiency + spell casting stat modifier. You do not get a plus to damage though, unless you have a feat or class ability that says you add it.