1. Which language is appropriate?
2. How can some one get me a sample programme so i can enter/i/os to suit my PLC?
I will try to answer both of your questions.
Presumably by "language" you are referring to what type of coding you will be doing, for instance - ladder logic. I don't think it makes much difference for MOST control projects as long as the guys who have to maintain it are able to do so. that is why ladder logic is so popular as it is pretty universal and there are a bazillion guys that can maintain such systems. If you are instead referring to language as English, German, etc., I would again suggest it be based on what language the people maintaining it use. It does me little good to get a program documented in Russian since I cannot read Russian.
As for sample programs, most manufacturers have sample programs available on their web sites.
I think you need to be more specific about your question. What type of PLC do you want to use? What type of level do you use? switch or transmitter?
I guess you are new in PLC. The first step is determine type of PLC you use, then you can learn about programming ladder.
A PLC is a controller only that (with the correct I/O) can handle a continuous level signal from a level transmitter. But only a couple PLCs in a market of hundreds has an integral HMI for displaying data. So programming a PLC for level also includes having and programming an HMI to display a level value.
There might be a more basic solution - no PLC, just a digital indicator.
Presumably the tank has a level measuring instrument with an electronic output. If the output is a typical industrial output like 0-5V or 4-20mA, then a digital indicator can be scaled to display either level or volume.