You can use ' for your string, so '"Something In Quotations"'
local exampleString = ' "sdknkadnka" ' -- You don't need to put spaces after the apostrophe's I just did that for visibility
print(string.find(exampleString, '"')
Your script is confused between the quotation marks that start and end the string, and those that are inside the string. There are two ways to solve this:
-- using single quotations
local exampleString = '"string"'
print(string.find(exampleString, '"'))
-- OUTPUT:
-- 1 1
-- using a backslash to avoid closing the string
local exampleString = "\"string\""
print(string.find(exampleString, "\""))
-- OUTPUT:
-- 1 1