For three years I have worked in tourism. Obviously, this field involves grave doubts concerning prohibited matters. I want to quit the job but I can not find another one. What is the ruling of the money I earned from this job after I quit it? May Allah reward you.

All praise is due to Allah. Peace and blessings be upon the Messenger of Allah. In fact, this question lacks details. If the questioner intends by tourism working in hotels or in public parks or resorts, as is the case in these good countries, this job is not wrong as long as it involves no sin. But if this tourism involves evil practices and preparations for prohibited matters or for drinking intoxicants, this is prohibited. I cannot give an absolute ruling without knowing the issue in detail. If the job is to provide general services to the visitors of the region, whether Muslims or non-Muslims, this job is permissible, and then the salary you take is permissible. But if the job is totally or mostly prohibited, this is not permissible.
Thus, if he is in need or poor, he may use this salary; but he has to look for another job, particularly if he is in a Muslim country, for these are not wholesome things. Considering the position of Abu Hanifah, we differentiate in some cases between working in Muslim countries and working in other countries. Hence, the issue lacks details. We advice the questioner to avoid sinful acts and prohibited matters in tourism and to take the side of innocent entertainment, for there is no harm in this as long as it involves no sin or illegitimate acts. Allah knows best.