Is there a way to change Cold damage to fire

Hi, i have on sceptre "+18 To cold damage over time multipler" do i can change that to "+18 to Fire damage over time multipler" ?? maybe on harvest or something like that

there is no way to change that, no.

cold to fire support gem ?

Unfortunately, you can't convert DoT from one type to another (https://www.poewiki.net/wiki/Damage_conversion).

Converting Cold Damage to Fire Damage is indeed possible - Cold to Fire support gem and Pyre just to name a few. Of course those changes do not apply to DoT as stated above - having 100% Cold to Fire conversion will change the hit damage of your Vortex to pure Fire, but the pool will still deliver Cold DoT

Your question is misleading. What you are actually asking is if there is a way to change the element of an elemental-related modifier on an item - in this case, +x% to cold DoT to +x% to fire DoT.

The answer is no. With the sole exception of Harvestcraft's change of elemental resistance modifiers on non-unique items into another element, it is impossible to change the "element" of a modifier

He claerly asked if he can change cold dot mod to fire dot mod on his weapon.
Is it THAT HARD to understand? Read entire post, not just the tittle and there wont be any "mislead".