If the EA logic is simple (e.g., Moving Average Cross, RSI, Martingale), pay a freelancer or use to rewrite it from scratch.
However, if you are looking for a "free top" tool to do this instantly, there is some important context you need to know about the current state of MetaTrader 4 security. The Reality of EX4 to MQ4 Conversion how to convert ex4 to mq4 free top
Manual decompilation requires advanced programming skills and knowledge of MQL4 language. If the EA logic is simple (e