How predicting the power consumption for a period of time?

Power consumption of what? More information is needed to answer the question.

Predicting power consumption of any single electrical load, is a matter of foreknowledge. e.g. How often will it be used and for how long , what is the diversity , what is the efficiency ,what is the power factor. This should be a relatively simple exercise.
However if the question is extended to predict maximum demand of multiple loads including load fluctuations this then requires a very different approach. So I would agree with Mr Gawler ' ..more information is needed ...' from Mr Hamadneh

Note so simple!. Please note that standards and definitions are different ( IEC or IEEE ) to define loading requirements and timing periods.
For example a comparison of the IEEE and IEC definitions will show that they are different. Demand as defined by the IEEE assumes that it is an average value for a
specified period of time while the same word as defined by the IEC is not necessarily an
average value for a specified period of time. Also, IEEE does not include a definition for installed load.
However, since it is mainly used to size electrical equipment at the start of a project , we have different rules for sizing feeders (US, NEC, CSA or Europe) and as in earlier comment made by Ross, there are based on code and different (hospitals, schools, dwellings ect...) and historical or metering data is very important. The objectives are the same, therefore there should be ONLY minor differences at the end and some care must be used to define the power cumsumption over a period of time.
However, without too many details:
The information should be described as a list of total loads by facility. The list should
include the installed load in kW (or MW), the connected load in kW (or MW), the demand
load in kW (or MW) and kVA (or MVA), and the annual energy consumption in MWh.
Where appropriate, the lists should also include the installed and connected loads in
horsepower. In addition, factors a such as demand, peak, average, diversity ,intermittent, continuous, PF, standby, emergency, ect... should be known for any facility.
This informations are required in order to prepare equipment sizing , load flow studies as well as electrical protection.

Thanks for us, but ineed in less words to answering of my question

I would do a load recording for 24-72 hrs. If you don't have the equipment or training you can hire someone to do it for you, then discuss it with them.

Perhaps the easiest way to predict power consumption is from historical data, if available. You have to compare similar periods (e.g. same season, same kind of day – working/week-end, same time of the day, etc.). If historical data is not available, than, of course you need to look at installed power, various usage quotients. You can also start from the power transformer you are supplied from: check its power (kW), divided it by, say, 2, and multiply by 24 (hours/day) – it will give you some rough estimate for one day.

calculate the individual power consumption of each load per hour, then the average usage per day, per week... and so on.

Tabulate the accumulative consumption and using a reasonable diversity factor. this should give you a good prediction of your annual consumption